Almost all previous psychophysiological research into antisocial and violent behavior suffers from the problems of using selected, institutionalized subject samples. This study aims to overcome these problems by testing theories of antisocial behavior within the context of a large prospective longitudinal study. The specific aims of this study are to assess whether (a) psychophysiological variables measured at age 11 are capable of predicting criminal behavior ascertained at age 22 (b) the interaction between social cognitive, and biological measures is important in understanding antisocial and violent behavior (c) violent offenders have a specific psychophysiological response pattern which differentiates them from non-violent offenders (d) female criminal behavior has a particularly strong psychophysiological basis (e) predictions generated by arousal, orienting, and information processing proficiency theories of antisocial behavior can be substantiated. Analyses will be carried out within the context of the Mauritius longitudinal project. A cohort of 1795 subjects from the general population on the island of Mauritius were psychophysiologically tested at age 3 years in 1972, and have been re-tested at ages 5, 11 and 17. At age 11 subjects were assessed on skin conductance, heart rate, EEG, and event-related potentials; variables from this phase will be used to test the above hypotheses. It is proposed to administer a modified version of a self-report delinquency scale to all subjects, and collect data from records of court convictions and police arrests to assess 'official' crime. These criminal behavior outcome measures will then be related to psychophysiological assessment measures at age 11, and social, cognitive, obstetric, and neuropsychological measures collected in other phases. Findings obtained from one half of the sample will be cross-validated on the second half. Results of this study will have implications for understanding the development of criminal behavior, and the early prediction of criminal and violent behavior.